Known stacking systems are configured to be used adjacent to a rotary die cut machine which cuts blanks (not illustrated) from sheets of material, for example, corrugated paperboard. The stacking system includes a receiving or “layboy” section that receives the sheets from the die cut machine and discharges them onto a transfer conveyor. The transfer conveyor carries the sheets to an inclined main conveyor, and the sheets travel along the main conveyor to its downstream end where they are discharged into a accumulator.
Die cut machines produce a certain amount of scrap material and dust during operation which scrap consists mainly of the portions of the input material that do not become part of a finished sheet. In addition, each sheet may include slots or through-openings. The material cut from the sheets to form these slots and through-openings also constitutes scrap.
Most scrap material produced by the die cut machine drops beneath or immediately in front of the die cut machine as it operates. However, it is not uncommon for a sheet to be cut incompletely so that portions of the sheet that were supposed to be removed instead travel into the layboy with the sheet. Excessive scrap in the transport path between the layboy section and the final stack of sheets may adversely affect the transport of the sheets. That is, the scrap may interfere with the alignment of the sheets or lead to jams. Alternately, if the scrap is carried all the way through the stacker and into the final stack of sheets, the sheets in the stack will have gaps therebetween where the scrap material is present thus resulting in a crooked, or oversized or non-uniform stack of sheets. Some scrap may even end up inside a finished box formed from the cut sheets; this is generally undesirable to most end customers and must be completely avoided in some applications, such as boxes for use to package food.
It is therefore known to provide various scrap removal devices in a stacking system. These may comprise, for example, brushes that gently contact a top and/or bottom surface of the moving sheets to dislodge the scrap and/or air jets directed against the sheets. In addition, dust can be created by the die cut process, and dust can be stirred up by the brushes and other elements intended to remove scrap from the sheets of material as they are moved along a conveyor system. It would be desirable to reduce the amount of dust present in a final stack of sheets as well as to reduce the amount of dust that enters the environment surrounding the stacking system.